Explosive containing oxidizing salt, organic nitro-compound, and hydrophilic colloid



(vide the, British Patent No. 597,716).

3,296,042 Patented Jan. 3, 1967 3 EXPLOSIVE CONTAINING OXIDIZING SALT,R-

GANICiNITRO-COMPOUND, AND HYDROPHIL- IC COLLOID ThereseQuadflieg,Frankfurham Main, Germany, and

\ Gustav Allan Wetterholm, Gyttorp, Sweden, assignors to. NitroglycerinAktiebolaget, a company of Sweden No Drawing. Filed Mar. 30,1964, Ser.No. 355,907

r 10 Claims. (Cl. 149-7) 1 This application is a continuation-in-part ofour applicationfierial No. 561,982 filed January 30, 1956, nowabandoned;

THE INVENTION BROADLY The present invention pertains to a plasticexplosive comprising a mixtureof a solid explosive of high brisancehaving, in :a highly compressed condition, a detonation velocityexceeding 7,500 m./ sec. and at least one oxygendelivering, inorganic:salt incorporated in a gel produced from water and a hydrophiliccolloid.

BACKGROUND OF THE INVENTION Plasticexplosives of this type arepreviously known They are produced .by first preparing a gel from wateras the liquid constituent while employing a hydrophilic colloid as thegel-forming substance. Into the inexplosive gel thus 1 formed ahigh-explosive compound and one or more oxygen-delivering inorganicsalts, such as nitrates and chlorates, are then kneaded. If desired,also other additional substances are added in suitable quantities.

Ini the patent referred to, there are set forth examples of explosiveshaving the following composition:

Example 5 Example 6 Example 7 Example 8 Gel former 5 5 3. 7 3. 9

Oxidizing salt 15. 5 24. 0 11. 4 20.0

Water 2. 8 6. 1 2. 4 3.1

Explosive of high brisance 64 65. 0 73. 5 73 All these explosives; arestrongly underbalanced with *respecttooxygen. Another characterizingfeature is that they have a high content of explosive of high brisance.When. testing them, it has been found that, especially initwo respects,they do not possess sufficiently satisfactory properties to render themutilizable under practical conditions. 1111 order to be a safetyexplosive, an explosive should fulfill two essential requirements,namely, it shall have a lowsensitivity to mechanical influences,especially impact, but, it must be easy to initiate. It is in these twowrespects that the known explosives have proved unsatisfactory.

The: following two examples will confirm this fact.

Example 1 1 An explosive according to Example 7 of the British PatentNo. 597,716, was made up:

. Percent Hexogem 73.5 Ammoniumnitrate 11.4 Ui'ea 5.7 Sodium acetate 3aq 3.4 \Sddiumthiosulfate 5 aq 2.3

Starch 3.7

The water content of the explosive was 1.66 percent. On firing thisexplosive containing increasing contents of water with detonator No. 4,the following test results were obtained:

' Contentspf water Number of tests Number of detonations 1n theexplosive, percent The above explosive, having a water content of 1.7%,was tested with respect of safety when being drilled on. These testswere carried out in such a way that drilling on an amount of 15-20 g. ofthe explosive inserted in a predrilled hole with a not preheated drillwithout crown was carried out for 60 seconds. Ten such tests werecarried out with this explosive.

Results Amount Test time, sec.

Number of tests Number of denotations Example 2 An explosive accordingto Example 6 of the British Patent No. 597,716 was made up:

Percent Pentaerythritoltetranitrate 65.0 Ammonium nitrate 9.9 Calciumdinitrate 4 aq 20.1 Starch 5.0

On drilling-on testing this explosive, the following results wereobtained:

Results Amount Test time, sec.

Number of tests Number of detonations THE OBJECT OF THE INVENTION Theobject of the present invention is to provide a plastic explosivecomposition of the above type having improved properties regarding thetwo factors above referred to, rendering them possible to use asexplosives with improved safety.

THE INVENTION It has now been found that if the composition of the aboveexplosives is changed insofar that the content of explosive of highbrisance is lowered to values in the range of from 20 to 45 percent and,in combination therewith, the explosives are oxygen-balanced, theresulting explosive will be much more insensitive to mechanicalinfluences, such as impact and drilling on, at the same time as it willmaintain its property of being readily initiated. A condition that thisresult should be obtained is that the explosive of high brisance shouldnot 'be a liquid nitrate ester. The explosive should thus be at leastmainly free from nitroglycol and nitroglycerine. While in the knownexplosives the presence of such esters is not a disadvantage, theimprovement according to the invention at least partially depends onabsence of such esters.

It has especially been found that a safety explosive of the above typecan be attained by an oxygen-balanced composition, in which the contentof solid explosive of high brisance is from about 20 to about 45 percentby weight and the content of inorganic salt from about to about 70percent by weight. The composition and amount of gel should be such thatthe water content of the explosive composition is within the range of3-25% by weight. Furthermore, as mentioned, the explosive compositionshould be oxygen-balanced, whereby the composition will be insensitiveto mechanical initiation even when being drilled on in a bore-hole.Despite its high content of water, the explosive composition andparticularly despite its lower content of solid explosive of highbrisance, the novel explosive compositions can be initiated with weakdetonators.

THE OXYGEN-DELIVERING SALT Suitable inorganic oxygen-delivering saltsare, especially such salts of alkali metals and alkaline-earth metals,for example, ammonium nitrate, calcium nitrate, sodium nitrate, bariumnitrate or other nitrates, also calcium chlorate, potassium perchlorate,ammonium perchlorate or other chlorates and perchlorates. Thesesubstances are added in such quantities that the explosive isoxygenbalanced, for example in quantities between the limits 10-70%,preferably 30-65% by weight.

THE EXPLOSIVE OF HIGH BRISANCE As examples of explosives with highbrisance used as components in the safety explosive according to theinvention among other pentyl, hexogen, nitromannite, ditrinitroethylureamay be mentioned. Generally, such explosives with high brisance areparticularly suitable which, when themselves in a highly compressedcondition-corresponding to a density substantially within the range1.45-1.65have a detonation velocity exceeding 7500 m./sec. The saidexplosive should be finely divided, but the degree of division is notcritical.

THE HYDROPHILIC COLLOID Examples of suitable hydrophile colloids forproducing the gel are starch and dextrin of different types,carboxymethyl cellulose, agar-agar, alginates, pectin, alkylcellulose,alkylhydroxylalkyl(ethyl)cellulose and other substances. One hydrophilecolloid which has proved especially effective is guar gum. The guar mayhave been cross-linked by treatment with a cross-linking agent such asborate or chromate ions under alkaline conditions. The main ingredientof this material is galactomannan the content of which may amount to78-82 percent, the balance being proteins fibers and moist. The quantityof the colloid in the explosive may vary between the limits 0.3 and 10%by weight.

OTHER POSSIBLE INGREDIENTS OF THE EXPLOSIVE COMPOSITIONS Further, theexplosive may contain small quantities of additional substances usuallyincluded in explosives, for example organic flour, such as wood flour orrye flour and the like.

In certain cases it may also be desirable to add further substanceswhich, without affecting the basic inventive principle, impart certainspecially desirable characteristics to the explosive, for example, withrespect to its resistance to cold, stability, etc. For this purposeadditions to the gel of eutectic salt mixtures may be employed, and ithas also been found advantageous for increasing the resistance to coldto add low molecular poly-hydric alcohols such as glycol or glycerin. Toincerase the safety during the mixing of the components, the explosivewith high brisance may be added in a partially phlegmatised form. Asphlegmatising agents paraffin wax and waxes may be mentioned, forexample. Moreover, a part of the final water content of the explosivemay be added in such a way that the explosives with high brisance areadded moistened with water.

The amounts of wax, paraffin wax and the like serving as phlegmatisingagents and/ or coating agents may suitably be within the range 0.5-3% byweight.

-It is, of course, also possible to divide the salts during themanufacture of the explosives in such a way that a part is added to thegel in the form of a eutectic mixture and another part in solid formtogether with the highexplosive, in which case the latter part may becoated with water-repelling agents, as indicated above, and may alsoconsist of ground salts.

PRACTICAL USE OF THE EXPLOSIVES The explosives according to theinvention have proved to be useful for all kinds of normal rockblasting, for bulldozing and as explosives for gaseous coal mines.Naturally, the composition of the explosive is to be adapted to thefield of utilization of the same.

PROPERTIES OF THE NOVEL PLASTIC EXPLOSIVE COM-POSITIONS The mostremarkable property of the novel plastic explosive compositions is thatthey, despite a relatively low content of explosive of high brisance anda relatively high content of water, still possess a high power ofinitiation while being extraordinarily insensitive to mechancalstresses, patricularly when being drilled on in a bore-hole. In thisconnection, it has been found that explosive compositions disclosed inthe above-mentioned British Patent No. 597,716 are, of course, sensitiveto weak detonators, when they contain small amounts of water. If thecontent of water of these explosives is increased to values covered bythe invention, the resulting explosive compositions will obtain asuccessively decreasing power of initiation. As will be evident from thetest results in Example 3, the explosives according to the inventionmaintain their property of being initiated by weak detonators.

Example 3 An explosive of the following composition was made up:

This explosive was admixed with different amounts of water so as. toobtain representative values for a water content of the explosivebetween 3 and 25 percent. On

firing these mixtures with a detonator N0. 4 the following results wereobtained:

Contents of water Number of in the explosive, Number of testsdetonations percent The same resuults were obtained when rather thanditrinitroeth ylurea other explosives of high brisance were used; .inthe explosive compositions according to the invention.

From a comparison between the explosive according to Example 1 above andthe present explosive it is evident thatgthe latter are more readilyinitiated for higher contents of water within the field covered by theinvention.

This explosive was subjected to the drilling-on test set forthin:Example 1. The following results were obtained:

Results Amount Test time, sec.

Number of tests Number of detonations Example An explosive of thefollowing composition was made up:-

This explosive was subjected to the drilling-on test set' forth inExample 1. The following results were obtained:

Results Amount Test time, sec.

Number of tests Number of detonations Example 6 An explosive of thefollowing composition was made up:

Percent Pentaerythritol tetranitrate 35.0 Parafiin 0.9 Ammonium nitrate43.5 Calcium dinitrate 10.7 Glycerine 4.3 Starch 1.0 Water 4.7

This explosive was subjected to the drilling-on test setforth inExample 1. The following results were obtained:

Results Amount, g. Test time, sec.

Number of tests Number of detonations Example 7 An explosive of thefollowing composition was made up:

This explosive was subjected to the drilling-on test set forth inExample 1. The following results were obtained:

Results Amount, g. Test time, sec.

Number of tests Number of detonations A series of further examples formanufacture of the explosives according to the invention are given belowin tabular form. All samples were produced in a Mac- Roberts mixer inquantities of about 7 kgs. For this purpose the gel was firstintroduced, whereupon stirring was started and the remaining componentswere kneaded into the gel.

The explosive characteristics were determined by the following tests:

The detonation velocity was measured in a camera with a rotating mirror.The small lead block test was carried out according to Hess but withonly 20 g. of explosive. The mortar values were obtained with aballistic pendulum ofstandard construction and were related to thetrotyl value (TNT). The gap tests were determined with cartridges, 25mm. in diameter, at 20 C. The stability values were determined bymeasuring the loss of weight at C. for a loss of weight of 1% in a fiaskof Pyrex glass having a diameter of 20 mm. and with a ground-incapillary of 0.2 mm. diameter and a length of 40 mm. Explosives madewith different kinds of starch yield very similar results.

Composition, percent by Weight Ex. Oxygen delivering salts No.Components besides water Highly Parafiin brisant Colloid PolyhydricOrganic wax, wax, H2O explosive NH4NO3 Ca(Na)2 alcohol flour etc.

or or NaNOs Ba(NOa)2 Pentyl, NH4NO3, Starch 42. 6 2. 8 12.0 Same as 832.0 5. 8 7. 8 Same as 8 21.0 8.2 7.3 Pentyl, NI'I4NO3, Pectin 42.4 3. 311.7 Dinitrinitroethylurea (DiTeU), 36. 0 3. 8 25.0

NH; N 0 Ethylhydroxyethylcellulose. 13 DiTeU, NH4NO treated with Wax,31. 1 51. 9 3. 6 1.2 1.1 11.2

(zlvarboxymethylcellulosa Wood flour,

ax. 14 DiTeU, NH NO3, treated with par- 42.5 41.6 2.8 0.9 12.2

affin wax, Ethylhydroxyethylcellnlose, Paraflin wax. 15 Hexogen,phlegmatised with 2.5% 40. 6 41. 7 1. 3 3. 2 1.0 12. 1

paraffin wax, N aN O3, Starch, Rye flour, Wax. 16 Nitromannite, moistStarch, NH4NOa, 33. 3 32. 5 14. 3 1. 3 8. 7 0. 5 9. 5

Ca(NO3)2 in eutectic salt mixture, Rye flour, Paraflin wax. 17 DiTeU,phlegmatised with 2.5% 36. 3 17. 5 24. 7 9. 7 0.9 10. 8

paraffin wax, NH NO3, C3.(NO3)z, Starch, Wax. 18 DiTeU, phleg'matisedwith 2.5% 36. 5 40. 5 11.1 1. 0 4. 2 1. 7 5.0

parafin wax, NH4NO3, Ca(NOa)z, Agar-agar, Wood flour, Paralfin wax. 19DiTeU, phlegmatised with 2.5% 41. 6 36. 1 10. 6 0. 9 5. 1 1. l 4. 6

paraffin wax, NH4NO3, C9.(NO3)2, Guar, Glycol, Wax. 20 DiTeU, moistenedto 10%, phlegma- 33. 5 47.0 7.0 0.8 3. 7 1.7 6.4

tised with 2.5% paraffin wax, NH4NO3, Ca(NOa)2, Glycol, Wax. 21 Peptyl,phlegmatised, N H4NO3, 35. 0 43. 5 10. 7 1. 0 4. 3 0.9 4. 7

Starch, Glycerin, Paraflin Wax. 22 DiTeU, phlegmatised With 2.5% 39.038. 5 3. 0 5. 5 1. 0 13. 0

paraflin wax, K0103, Starch, Glycol. 23 DilcU, phlegrnatised with 2.5%par- 39.0 33. 5 3.0 1. 5 1.0 22.0

aflin wax, Ba(NOs)2, Starch, Glycol, Parafin wax.

Impact Tests of explosive characteristics sensitivity Stability test,per- Excess of Cartridge, at 80 0., Ex. cent det- Consistency oxygen,Volume Detonation velocity Small lead Mortar Gap test 1% short N o.onation percent weight, (camera) block test test, per- (25 mm. weightper cm. g. /cm. according cent of cartridge) after length of to Hess (20TNT mm. honrs fall Density M./s. g.), mm.

8 0/60 Plastic 0. 9 1. 47 1. 42 6, 100 29. 0 126 70-90 360 1. 51 6, 60012 0/60 Plastic to semiplastic 1.1 5,200 16.5 93 0 13 0/60 Plastic 1.2 1. 43 2 6, 200 16. 5 116 20-30 10 Example 24 Composition, percent byweight Oxygen delivering salts Components besides water Highly brisantColloid Polyhydric explosive NHrHNa or Ca(N0a)z 0r alcoh NaNO Ba(N0s)2or chlorate DiIeU, phlegmatised with 2.5% garafi'ln wax, NH4 104, NaNOa,Starch, Glycol 39.4 17. 0 23.6 2. 0 7, 1

What we claim is:

1. HA novel plastic explosive having low sensitivity when beingdrilled-on in combination with ease and reliability of detonation byweak blasting caps mainly consisting of (a). from about 20 to about 45%by weight of a finely divided solid explosive ingredient of highbrisance selected from the group consisting of pentyl, hexogen,nitrornannite, ditrinitroethylurea and having ,at a density above 1.45g./cc. and detonation velocity exceeding: about 7500 m./second;

(b): at least one oxygen-delivering inorganic salt selected from thegroup consisting of nitrates, chlorates; and perchlorates of alkalimetals and alkaline earth metals in an amount of from about to about 70%by weight, and

(c). a gel produced from water and a hydrophilic colloid selectedfromthe group consisting of starch, dextrin, 1 carboxymethyl-cellulose,agar-agar, alginates, pectin, ,alkyl cellulose, alkyl-hydroxyalkyl(ethyl) cellulose, guar gum and cross-linked guar gum, the compositionand the amount of said gel being such that the water content of theexplosive is within the range of from about 3 to about 25% by weight andthe hydrophilic colloid ranges between about :0.3.and 10%by weight,

said composition being oxygen-balanced and substantially free fromliquid esters of nitric acid.

2..1An explosive .composition according to claim 1 Whereinysaidfinely-divided solid explosive ingredient of high brisance isditrinitroethylurea.

3.An explosive composition according to claim 1 whereinusaidfinely-divided solid explosive ingredient of high brisance is pentyl.

4.11An explosive .composition according to claim 1 Example 24-ContinuedComposition, percent by weight Impact sensitivity test, Excess ofoxypercent deto- Consistency gen, percent Organic flour Paraffin wax, HO nation per cm.

wax, etc. length of fall None 1. 0 9. 9 Plastic 1. 0

Tests of explosive characteristics Stability at Cartridge, volumeDetonation velocity Small lead 8 0., 1%

weight gJem. (camera) block test Mortar test, Gap test short weightaccording to percent of (25 mm. carafter hours Hess (20 g.) TNT tridge)mm. Denslty M./s. mm.

wherein the amount of oxygen-delivering inorganic salt is from about 30to about by weight.

5. An explosive composition according to claim 1 wherein the colloid isstarch.

6. An explosive composition according to claim 1 wherein the colloid isguar gum.

7. An explosive composition according to claim 1 wheren the explosiveingredient of high brisance is present in a partially phlegmatisedcondition.

8. An explosive composition according to claim 1 wherein the inorganicsalt is at least partly ammonium nit-rate.

9. An explosive composition according to claim 1 wherein the salt is atleast partly coated with a waterrepelling substance selected from thegroup consisting of wax, paraifin wax and silicones.

10. An explosive composition according to claim 1 which additionallycontains an antifreezing agent selected from the class consisting ofglycol and glycerine.

References Cited by the Examiner UNITED STATES PATENTS 2,048,050 7/1936Baker 149-7 2,167,679 8/1939 Rinkenbach et al 149-92 2,548,693 4/ 1951Whetstone et a1 149-47 2,817,581 12/1957 Rinkenbach et al. 14947 FOREIGNPATENTS 597,716 2/ 1948 Great Britain.

CARL D. QUARFORTH, Primary Examiner.

BENJAMIN R. PADGETT, Examiner.

S. I. LECHERT, JR., Assistant Examiner.

1. A NOVEL PLASTIC EXPLOSIVE HAVING LOW SENSITIVITY WHEN BEINGDRILLED-ON IN COMBINATION WITH EASE AND RELIABLITY OF DETONATION BY WEAKBLASTING CAPS MAINLY CONSISTING OF (A) FROM ABOUT 20 TO ABOUT 45% BYWEIGHT OF A FINELY DIVIDED SOLID EXPLOSIVE INGREDIENT OF HIGH BRISANCESELECTED FROM THE GROUP CONSISTING OF PENTYL, HEXOGEN, NITROMANNITE,DITRINITROETHYLUREA AND HAVING AT A DENSITY ABOUT 1.45 G./CC. ANDDETONATION VELOCITY EXCEEDING ABOUT 7500 M./SECOND; (B) AT LEAST ONEOXYGEN-DELIVERING INORGANIC SALT SELECTED FROM THE GROUP CONSISTING OFNITRATES, CHLORATES, AND PERCHLORATES OF ALKALI METALS AND ALKALINEEARTH METALS IN AN AMOUNT OF FROM ABOUT 10 TO ABOUT 70% BY WEIGHT, AND(C) A GEL PRODUCED FROM WATER AND A HYDROPHILIC COLLOID SELECTED FROMTHE GROU PCONSISTING OF STARCH, DEXTRIN, CARBOXYMETHYL-CELLULOSE,AGAR-AGAR, ALGINATES, PECTIN, ALKYL CELLULOSE, ALKYL-HYDROXYALKYL(ETHYL) CELLULOSE, GUAR GUM AND CROSS-LINKED GUAR GUM, THE COMPOSITIONAND THE AMOUNT OF SAID GEL BEING SUCH THAT THE WATER CONTEND OF THEEXPLOSIVE IS WITHIN THE RANGE OF FROM ABOUT 3 TO ABOUT 25% BY WEIGHT ANDTHE HYDROPHILIC COLLOID RANGES BETWEEN ABOUT 0.3 AND 10% BY WEIGHT, SAIDCOMPOSITION BEING OXYGEN-BALANCED AND SUBSTANTIALLY FREE FROM LIQUIDESTERS OF NITRIC ACID.
 9. AN EXPLOSIVE COMPOSITION ACCORDING TO CLAIM 1WHEREINN THE SALT IS AT LEAST PARTLY COATED WITHA WATERREPELLINGSUBSTANCE SELECTED FROM THE GROUP CONSISTING OF WAX, PARAFFIN WAX ANDSILICONES.